Progress towards the development of a vaccine for HIV has been hindered by the limited number of animal models with which to study HIV infection of humans. Simianimmunodeficiency virus (SIV) infection of the rhesus macaque is perhaps the best animal model with which to study HIV infection of humans. Although several vaccines tested in rhesus ,acaques have provided protection against SIV challenge, it has not been possible to determine the correlates of protection in these vaccine trials. However, since there is a storng cytotoxic T lymphocyte (CTL) response to the AIDS virus in both humans and rhesus macaques, CTLs have been implicated in providing protection from infection. Understanding the importance of CTLs in AIDS virus-induced disease will therefore, be crucial for the design of an effective vaccine. Unfortunately, few CTL epitopes have been defined in SIV, and furthermore, there are no inbred strains of rhesus macaques for CTL adoptive transfer studies. In this proposal, we will triple the number of well-defined SIV CTL epitopes and will develop a rapid method for the MHC class I-typing of rhesus macaques. We will produce pairs of MHC-identical rhesus macaques to explore the role of CTLs in AIDS virus infection. We will also generate pairs of MHC-defined, identical rhesus macaques for CTL adoptive transfer studies, critical for understanding the correlates of immune protection. In the first specific aim of this proposal, we will define six new SIV CTL epitopes (two in env and four in nef). We will determine the anchor residues, the minimal recognizable peptide and the MHC class I molecules that bind these epitopes. We will also develop a PCR-SSP-based technique for detecting all nine of the restricting rhesus macaque MHC class I alleles. In the second specific aim of this proposa, we will generate MHC-defined pairs and MHC-defined, identical pairs of rhesus macaques using embryo and nuclear transfer technologies. We have identified two MHC typed macaques with strong SIV-specific CTLs against multiple epitopes in an extended family of rhesus macaques. We will use oocytes from relatives of these SIV-infected monkeys to produce embryos by in vitro fertilization (IVF) and nuclear trasnfer. This iwll enable us to generate pairs of age-matched, MHC-defined and MHC-defined identical animals in a short period of time. In the MHC-identical offspring from the embryo transfer experiments, we will be able to induce CTL against multiple epitopes in uninfected animals and subsequently challenge these animals with SIV. In the nuclear transfer experiments, the creation of MHC-defined pairs of identical animals will allow us to carry out CTL transfer experiments in the rhesus macaque for the first time. These advances in a relevant primate model will be important in the development of an AIDS vaccine.